There has been continuing interest in organic materials which can function as additives for modifying or improving the flavor and aroma and other properties of smoking compositions, e.g., additives such as flavorants and humectants.
Numerous nitrogen containing compounds have been isolated from tobacco and tobacco smoke [c.f. I. Schmeltz and D. Hoffmann, Chem. Rev., 77, 295 (1977); R. L. Stedman, Chem. Rev. 68, 153 (1968); G. B. Neurath, Beitr. Tabakforsch., 5, 115 (1969)] and many of these are known to be important to tobacco flavor. Of particular importance and significance are nitrogen heterocycles such as pyrazines and pyridines, their alkyl derivatives and their heteroatom derivatives.
Thus, it has been established that alkyl-pyrazines are natural components of tobacco smoke, and that they most probably are important contributors to tobacco smoke flavor [A. Baggett et al, J. Chromatog, 97 79 (1974)]. Further, it has been disclosed in the patent literature that addition of alkylpyrazines to tobacco results in an improvement in the flavor of smoking compositions as perceived by a test panel.
British Pat. No. 1,244,068 describes a method for influencing the smoke flavor of tobacco or a tobacco mixture which consists of treating the tobacco with a pyrazine derivative of the following chemical structure: ##STR2## in which each R is independently a hydrogen atom, an aliphatic radical, an alicyclic radical or an aromatic hydrocarbon radical, such radicals having up to 9 carbon atoms, or R is a heterocyclic radical containing 4 to 9 carbon atoms.
U.S. Pat. No. 3,402,051 describes a process for imparting a popcorn-like flavor and aroma to tobacco and foodstuffs by the incorporation of a 2-acetylpyrazine derivative therein.
Other patents which disclose the addition of various pyrazine compounds to tobacco and foodstuffs as a means of providing flavor or flavor enhancement include U.S. Pat. Nos. 3,684,809; 3,705,158; 3,754,934; 3,764,349; 3,767,426; and 3,881,025.
U.S. Pat. No. 3,914,227 discloses pyridyl and pyrazyl ketones and their use in altering the organoleptic properties of tobacco and foodstuffs, and U.S. Pat. No. 4,166,869 discloses acylpyrimidines useful as flavorants for the same type of applications.
Alkylpyridines have also been found to be useful tobacco additives. As an example, U.S. Pat. No. 3,625,224 describes the use of methylpyridines, ethylpyridines and various dialkylpyridines as tobacco additives. U.S. Pat. No. 3,381,69 discloses 2-methyl-5-isopropylpyridine as a tobacco additive.
It is characteristic of pyridine, pyrazine, pyrimidine and other heterocyclic derivatives employed as tobacco flavorants in the prior art, as illustrated by the above described technical literature, that the respective heterocyclic derivatives have the disadvantage of both high volatility and low odor threshold. Both of these properties significantly restrict the extent that these heterocyclic derivatives can be utilized as flavorants in tobacco compositions. A quantity of a pyrazine or pyridine derivative in a tobacco composition sufficient to have a noticeable effect in low delivery cigarettes causes a marked pack aroma.
When an aldehyde flavorant such as cinnamaldehyde is added to a smoking composition, the loss of the flavorant during the manufacturing process and during storage is high, due to the relatively high vapor pressure of the aldehydic compound.
Further, as described in U.S. Pat. No. 3,782,391 alkyl esters of beta-methyl valeric acid are known to impart a fruity, apple-like aroma and a nut-like flavor when incorporated in tobacco. However, as noted in U.S. Pat. No. 3,854,485, such flavorant compounds are relatively valuable substances with a low odor threshold, and they present an evaporation problem in prolonged storage of the flavored tobacco compositions. Other esters such as monoalkyl and dialkyl malonates are known to provide a tobacco smoke with a fermented apple-peel and walnut-like flavor and aroma, but such esters yield only a limited form of flavor enhancement in tobacco products.
U.S. Pat. No. 4,036,237 endeavors to overcome some of the disadvantages of the above-described flavorant technology. The said patent provides for the incorporation in smoking compositions of a flavorant compound which imparts cherry-like or fruity flavor to the smoke thereof, which flavorant compound is not lost during the manufacture and storage of the flavored smoking composition, and which is readily released when the smoking composition is burned. Illustrative of a U.S. Pat. No.4,036,237 flavorant compound is ethyl 2,2-dimethyl-3-hydroxy-3-phenylpropionate.
Other prior art is concerned with the incorporation into tobacco fillers of additives having humectant properties for the retention of moisture and the prevention of staleness in smoking compositions.
U.S. Pat. No. 1,407,274 proposes a method of improving the moisture-retaining properties of tobacco by incorporating a 1,2-glycol such as ethylene glycol into the tobacco matrix.
U.S. Pat. No. 1,954,109 discloses a method of preparing a smoking composition which consists of coating a tobacco filler with a water solution of a gelatinous material which tends to retain moisture in the tobacco.
U.S. Pat. No. 1,961,866 describes a method of controlling the moisture content of tobacco which involves incorporating pectin in the tobacco to function as a humectant.
U.S. Pat. No. 2,286,639 proposes the use of ammoniated aldose as an anti-staling agent in tobacco compositions. U.S. Pat. No. 2,114,281 describes the incorporation of a strongly absorbent material such as alumina hydrogel in tobacco. The absorbent retains water, and releases it under smoking conditions.
U.S. Pat. No. 2,788,372 describes the preparation of a sorbitol/1,2-alkylene oxide condensation product which is recommended as a humectant for stabilizing the moisture content of tobacco, cosmetics, paper products, and the like. U.S. Pat. No. 2,438,418 proposes the use of alpha-methylglycerine as a tobacco humectant which does not product toxic combustion products under smoking conditions.
Other prior art publications which provide background perspective for the present invention are those which relate to the presence of quaternary ammonium compounds as components of smoking tobacco compositions. In some cases the quaternary ammonium compound is formed in situ by treatment of the tobacco, and in other cases the quaternary ammonium compound is incorporated in the tobacco filler as an additive.
For example, U.S. Pat. No. 1,842,266 describes a method for alleviating the undesirable effects of tobacco by incorporating Vitamin B (thiamine hydrochloride) into the tobacco composition prior to smoking.
U.S. Pat. No. 1,941,416 discloses a method for neutralizing the properties of tobacco smoke which irritate the mucous membranes. The proposed method involves the incorporation of diamino-methylacridinium chloride in tobacco filler, which quaternary compound volatilizes under smoking conditions into mainstream smoke.
French Pat. No. 1,583,052 proposes the incorporation of a cationic surfactant in tobacco filler to function as a tar and nicotine absorbent under smoking conditions. One type of surfactant which is disclosed corresponds to the formula: ##STR3## where R.sup.6 is an acyclic hydrocarbon radical containing 10-22 carbon atoms, R.sup.1 is a lower hydrocarbon such as methyl or ethyl, and X is a halogen or sulfate anion. Also disclosed are pyridinium salts containing the same R.sup.6 substituent and X anion as defined above. The R.sup.6 substituent according to French Pat. No. 1,583,052 contains at least ten carbon atoms and contributes a fat-solubility property to the surfactants.
As an example of in situ formation of a quaternary ammonium compound in tobacco filler, U.S. Pat. No. 2,985,549 describes a method of forming alkyl nicotinium halide in tobacco by treating the tobacco with an alkyl halide reagent such as methyl chloride. The said treatment of tobacco filler is said to lower the tar and nicotine content of mainstream smoke under smoking conditions.
Bach et al in Fachliche Mitt. Oesterr, Tabakregie, 4, 53(1963), as summarized in C.A., 60, 868(1964), report a method for reducing the nicotine content of tobacco by treating the tobacco with ethylene oxide to convert the nicotine into a N-(.beta.-hydroxyethyl)-3-(N-methyl-2-pyrrolidinyl)pyridinium salt derivative.
Similarly, Obi et al in Tob. Sci., 12 70(1968) report a study of the reaction products of nicotine with ethylene oxide in tobacco leaves. In vitro experiments indicated that a quaternary ammonium compound such as N-hydroxyethylnicotine dihydrochloride under pyrolysis conditions at 600.degree. C. yield products such as nicotine, pyridine, 3-ethylpyridine, 3-cyanopyridine and quinoline.
As indicated by the foregoing description of prior art, there is continuing research effort dedicated to the development of smoking compositions which deliver controlled mainstream smoke compositions, and which provide a sensory satisfying level of pleasant flavor and aroma.
Accordingly, it is a main object of this invention to provide low tar and nicotine delivery smoking compositions which have desirable flavor and aroma characteristics as perceived by experienced smokers.
It is another object of this invention to provide smoking compositions which have incorporated therein a quaternary ammonium additive compound which is characterized by low volatility and low pack aroma.
It is another object of this invention to provide smoking compositions of tobacco and/or tobacco-substitute materials containing a quaternary ammonium compound as a flavorant additive, which additive is adapted to impart improved flavoring to the mainstream smoke and improved aroma to the sidestream smoke under smoking conditions.
It is a further object of this invention to provide smoking compositions containing a quaternary ammonium compound as a humectant flavorant additive, which additive is adapted to function as a moisture control and anti-staling agent during the preparation and storage of the smoking compositions.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.